1. Field of the Invention
The present invention relates generally to an optical information record member, and is directed more particularly to an optical information record member suitable to make an optical information carrier and for use as an optical video disc, digital audio disc which is used in a system in which the record on the carrier is read out in an optical manner.
2. Description of the Prior Art
An example of the prior art reproducing apparatus, which reproduces an optical information recorded on an optical information carrier such as a video disc by the reflection manner, is depicted in FIG. 1. In this example, an optical information carrier 1 such as a video disc is rotatably supported about an axis 0 and, for example, a He-Ne laser tube 2 is provided to emit a laser beam 3 as a read-out light. This laser beam 3 is irradiated through, for example, a lens 4, a polarized beam splitter 5, a quarter plate 6, a tangential mirror 7, a tracking mirror 8 and an objective lens 9 on the optical information record surface, for example, concave-convex record surface of the video disc 1. The reflected light beam on the concave-convex surface of the video disc 1, which is modulated by the interference between reflected light beam is introduced through the objective lens 9, mirrors 8, 7, quarter plate 6 and polarized beam splitter 5 to a detector 10 such as a photo-diode which then converts the light beam into an electrical signal. Hence, the optical information recorded on the video disc 1 is optically reproduced.
In such optical information carrier 1, for example, video disc, as shown in FIG. 2, on a substrate 11 which is transparent to the read-out light such as the laser beam 3 (which will be referred hereinafter to as a light permeability) there is formed, for example, a pit i.e. concave-convex surface as an information record surface 14 on which a reflection coating made of, for example, an Al layer is formed. A protective resinous coating 13 of the U.V. hardening acrylic resin is coated on the reflection coating 12.
A method to provide such an information record carrier is a press-mold method. At first the press-mold method will be now described with reference to FIGS. 3 to 11. By this method, a master 20 is prepared first as shown in FIG. 3. The master 20 consists of, for example, a glass substrate 21 and a concave-convex surface 22 made of, for example, a photo-resist layer which is provided with recesses or cut-outs corresponding to pit portions of an information record surface of an information record carrier finally obtained by the irradiation of the laser beam which is modulated by the information signal to be recorded. The above concave-convex surface 22 may be formed by such a manner that the photo-resist layer is selectively exposed to the modulated laser beam and then non-exposed portions of the photo-resist layer are etched away.
Then, as shown in FIG. 4, for example, nickel is coated on the master 20 by electroless plating and subsequent electro-plating or the like to prepare a metal master 24 which comprises a convex-concave surface 23 corresponding to the concave-convex surface 22 on the master 20.
Then, the metal master 24 is peeled off from the master 20 as shown in FIG. 5.
Next, as shown in FIG. 6, metal plating, by way of example, is carried out on the convex-concave surface 23 of the metal master 24 to provide a mother 26 which comprises a concave-convex surface 25 corresponding to the convex-concave surface 23.
The mother 26 is peeled off from the metal master 24, as shown in FIG. 7.
As shown in FIG. 8, metal plating is further carried out on the mother 26 to provide a stamper 28 which has a convex-concave surface 27 corresponding to the concave-convex surface 25 of the mother 26.
The stamper 28 is then peeled off from the mother 26 as shown in FIG. 9.
By using the stamper 28 thus manufacture, thermo-plastic resin such as acrylic resin or the like is press-molded to provide a substrate 11 of the information record carrier on which a concave-convex information record surface 14 is formed as shown in FIG. 10.
Then, the substrate 11 is peeled off from the stamper 28 and then a reflection layer 12 made of, for example, Al is coated on the information record surface 14 of the substrate 11, and further a protective resinous coating 13 is formed on the reflection layer 12 as shown in FIG. 11. By this manner, the optical information carrier described in connection with FIG. 2 is provided.
According to the above method, since the concave-convex surface, which is to be the information surface, is successively transferred from the master to the metal master, the mother and the stamper, the information surface of the finally provided optical information record carrier 1 does not always represent high fidelity and the process thereof is rather complicated. The reason is as follows. In order to manufacture from one precisely prepared master a plurality of stampers which are abraded much, at first one master is prepared, then a plurality of mothers are provided from the master and then a plurality of stampers are provided from each of the plurality of mothers.
Further, in the above prior art method, in preparing the metal master, mother, and stampers, electroless plating and electro-plating are utilized, which takes a long time. This results in poor manufacture efficiency.